Learn Arabic (Modern Standard): أين المبشرة الوردية؟

It follows the مِفْعَلَة (mif'alah) pattern, which is a common "noun of instrument" (a word for a tool). It is built from the root ب-ش-ر (to grate or scrape), so مبشرة literally means "a tool used for grating." Other common tools using this pattern include مكنسة (broom) and ملعقة (spoon).

The word for "pink" here is الوردية. Isn't that derived from the word for "roses"?

Exactly. While primary colors have their own specific grammatical pattern (like أحمر for red), many secondary colors in Arabic are formed using a "Nisba" adjective by adding the suffix ـيّ (-iyy) to a noun. Since ورد (ward) means "roses", ورديّ (wardiyy) means "rose-colored" or "pink". It takes the feminine ـة here to match the noun.

Doesn't the root ب-ش-ر also mean "good news" or "humans"? How does it relate to a grater?

Arabic roots often have fascinating semantic shifts! The original, physical meaning of ب-ش-ر is to peel, scrape, or shave the surface of something (hence مبشرة for a grater). Because skin is the "surface" of a body, the root gave rise to بشرة (skin or complexion) and بشر (mankind). The "good news" meaning stems from the idea of a person's face changing or "lighting up" upon hearing it.

If I were reading this sentence with full formal case endings (tashkeel), what would they be?